#include "MT19937.h"

void MT19937::Init(unsigned int s){
	mt[0]= s & 0xffffffffUL;
	for (mti=1; mti<N; mti++) {
		mt[mti] = 
			(1812433253UL * (mt[mti-1] ^ (mt[mti-1] >> 30)) + mti); 
		/* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
		/* In the previous versions, MSBs of the seed affect   */
		/* only MSBs of the array mt[].                        */
		/* 2002/01/09 modified by Makoto Matsumoto             */
		mt[mti] &= 0xffffffffUL;
		/* for >32 bit machines */
	}
}

void MT19937::Init(unsigned int init_key[], int key_length){
	int i, j, k;
	Init(19650218UL);
	i=1; j=0;
	k = (N>key_length ? N : key_length);
	for (; k; k--) {
		mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1664525UL))
			+ init_key[j] + j; /* non linear */
		mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
		i++; j++;
		if (i>=N) { mt[0] = mt[N-1]; i=1; }
		if (j>=key_length) j=0;
	}
	for (k=N-1; k; k--) {
		mt[i] = (mt[i] ^ ((mt[i-1] ^ (mt[i-1] >> 30)) * 1566083941UL))
			- i; /* non linear */
		mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
		i++;
		if (i>=N) { mt[0] = mt[N-1]; i=1; }
	}

	mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */ 
}

unsigned int MT19937::Rnd(){
	unsigned long y;
	const unsigned long mag01[2]={0x0UL, MATRIX_A};
	/* mag01[x] = x * MATRIX_A  for x=0,1 */

	if (mti >= N) { /* generate N words at one time */
		int kk;

		//if (mti == N+1)   /* if init_genrand() has not been called, */
			//init_genrand(5489UL); /* a default initial seed is used */

		for (kk=0;kk<N-M;kk++) {
			y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
			mt[kk] = mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1UL];
		}
		for (;kk<N-1;kk++) {
			y = (mt[kk]&UPPER_MASK)|(mt[kk+1]&LOWER_MASK);
			mt[kk] = mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
		}
		y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
		mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1UL];

		mti = 0;
	}

	y = mt[mti++];

	/* Tempering */
	y ^= (y >> 11);
	y ^= (y << 7) & 0x9d2c5680UL;
	y ^= (y << 15) & 0xefc60000UL;
	y ^= (y >> 18);

	return y;
}
